Reacting a phenol with formaldehyde in the presence of an acidic catalyst is generally known as a reaction for manufacturing phenolic novolak resin and the like. On the other hand, manufacturing polyphenol (Japanese Patent Publication No. H06-001741 A) or novolak resin (Japanese Patent Publication No. 2004-511584 A) by reacting aldehydes, such as acetaldehyde, propionaldehyde, isobutyraldehyde, crotonaldehyde, or benzaldehyde, has also been demonstrated.
It is known that novolak resin can be manufactured by reacting hydroxybenzaldehyde or the like, which has the properties of both a phenol and an aldehyde (Japanese Patent Publication No. 2008-088197 A).
These polyphenols and novolak resin are used as coating agents or resist resins for semiconductors. One desired property for such uses is heat resistance. It is generally known that heat resistance can be improved by enhancing the carbon concentration in resin. One method for enhancing the carbon concentration and reducing the oxygen concentration is to introduce an aromatic hydrocarbon component. One such known component is a polymer (acenaphthene resin) having the structure shown by the following formula (Japanese Patent Publication No. 2000-143937 A).
In the formula, R1 is a monovalent atom or group, n is an integer from 0 to 4, and R2 through R5 are either independent hydroxy groups or are monovalent atoms or groups.
Such materials, however, have problems such as being expensive, requiring strict reaction conditions in order to obtain resin, or involving many, complex reaction processes.
On the other hand, in the manufacture of semiconductor devices, microfabrication is performed via lithography using a photoresist composition. In recent years, along with a shift to high integration and high speed of LSIs, demand has increased for further refinement by pattern rules. However, within lithography by light exposure, which is a general technique at present, an inherent limit is being reached on the resolution derived from the wavelength of the light source.
As the light source for lithography used during resist pattern formation, a transition is being made to a shorter wavelength, from a KrF excimer laser (248 nm) to an ArF excimer laser (193 nm). As refinement of the resist pattern proceeds, however, the problem of resolution or the problem of the resist pattern collapsing after development occurs, leading to a desire for a resist with a thinner film. In this case, it becomes difficult to obtain a film thickness of the resist pattern sufficient for substrate processing, thereby requiring a process to allow not only the resist pattern but also a resist underlayer film, which is formed between the resist and the semiconductor substrate to be processed, to function as a mask during substrate processing. Currently, as the resist underlayer film for such a process, there is demand for a resist underlayer film for lithography having a dry etching speed selectivity near that of the resist, a resist underlayer film for lithography having a dry etching speed selectivity smaller than that of the resist, and a resist underlayer film for lithography having a dry etching speed selectivity smaller than that of the semiconductor substrate, unlike a conventional resist underlayer film with a high etching speed. (For example, see Japanese Patent Publication No. 2004-177668 A, Japanese Patent Publication No. 2004-271838 A, and Japanese Patent Publication No. 2005-250434 A.)
By virtue of having high etching resistance, a material with high carbon concentration is considered effective, and as such a material, an amorphous carbon underlayer film formed from CVD using material such as methane gas, ethane gas, acetylene gas, or the like is well known. From the perspective of processing, however, there is a demand for an underlayer film material that can be formed by spin-coating.
Furthermore, the present inventors have proposed an underlayer film forming composition consisting of a naphthalene formaldehyde polymer as material with high etching resistance and high solvent solubility (see International Publication No. WO 2009-072465 A). There is a demand for improvement, however, with respect to etching resistance with the technique in International Publication No. WO 2009-072465A.
Therefore, there is a desire for the development of a technique that can maintain the balance between etching resistance and solvent solubility to a higher degree.
Therefore, there is a desire for the development of a technique that can maintain the balance between etching resistance and solvent solubility to a higher degree.